Ab initio quantum chemistry of high-temperature superconductors

We developed an ab initio quantum chemistry framework for faithful simulations of high-temperature superconductors (cuprates). The method allows for spin SU(2) and particle-number U(1) symmetry-breaking states such that the superconducting orders spontaneously emerge during the self-consistency. We directly computed the superconducting pairing order of several doped cuprate materials and structures. We found that we could correctly capture two well-known trends: the pressure effect, where the pairing order increases with intra-layer pressure, and the layer effect, where the pairing order varies with the number of copper-oxygen layers. From these calculations, we observed that the strength of superexchange and the covalency at optimal doping are the best descriptors of the maximal pairing order. Our microscopic analysis further identified short-range copper spin fluctuations, together with multi-orbital charge fluctuations, as central to the pairing trends. Our work demonstrates the possibility of a quantitative computational understanding of high-temperature superconducting materials.